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Universal Correlations of Nuclear Observables and the Structure of Exotic Nuclei

Description: Despite the apparent complexity of nuclear structural evolution, recent work has shown a remarkable underlying simplicity that is unexpected, global, and which leads to new signatures for structure based on the easiest-to-obtain data. As such they will be extremely valuable for use in the experiments with low intensity radioactive beams. Beautiful correlations based either on extrinsic variables such as N{sub p}N{sub n} or the P-factor or correlations between collective observables themselves have been discovered. Examples to be discussed include a tri-partite classification of structural evolution, leading to a new paradigm that discloses certain specific classes of nuclei, universal trajectories for B(E2: w{sub 1}{sup +} {r_arrow} 0{sub 1}{sup +}) values and their use in extracting hexadecapole deformations from this observable alone, the use of these B(E2) values to identify shell gaps and magic numbers in exotic nuclei, the relationship of {beta} and {gamma} deformations, and single nucleon separation energies. Predictions for nuclei far off stability by interpolation will also be discussed.
Date: Autumn 1996
Creator: Casten, R. F. & Zamfir, N. V.
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Partner: UNT Libraries Government Documents Department
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Determining (n,f) cross sections for actinide nuclei indirectly: An examination of the Surrogate Ratio Method

Description: The validity of the Surrogate Ratio method for determining (n,f) cross sections for actinide nuclei is examined. This method relates the ratio of two compound-nucleus reaction cross sections to a ratio of coincidence events from two measurements in which the same compound nuclei are formed via a direct reaction. With certain assumptions, the method allows one of the cross sections to be inferred if the other is known. We develop a nuclear reaction-model simulation to investigate whether the assumptions underlying the Ratio approach are valid and employ these simulations to assess whether the cross sections obtained indirectly by applying a Ratio analysis agree with the expected results. In particular, we simulate Surrogate experiments that allow us to determine fission cross sections for selected actinide nuclei. The nuclei studied, {sup 233}U and {sup 235}U, are very similar to those considered in recent Surrogate experiments. We find that in favorable cases the Ratio method provides useful estimates of the desired cross sections, and we discuss some of the limitations of the approach.
Date: May 22, 2006
Creator: Escher, J E & Dietrich, F S
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Partner: UNT Libraries Government Documents Department
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A primer on rotational collective enhancements in even-even nuclei

Description: The enhancement of the level density for deformed nuclei relative to the level density in spherical nuclei is calculated. The qualitative behavior of the enhancement factor as a function of excitation energy is explained, and a prescription for a more quantitative description of this behavior is suggested. The results presented here can be found elsewhere in the literature, however the treatments of this topic are dispersed in the literature, are often terse, and require some familiarity with disparate branches of physics. The emphasis of this paper is on step-by-step derivations of the physics and mathematics used in the calculation of level densities and rotational enhancement factors. Pertinent techniques from thermodynamics and group theory are introduced. Appendices provide detailed introductions to the principal mathematical tools.
Date: July 15, 2004
Creator: Younes, W
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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CCN Spectral Measurements

Description: Detailed aircraft measurements were made of cloud condensation nuclei (CCN) spectra associated with extensive cloud systems off the central California coast in the July 2005 MASE project. These measurements include the wide supersaturation (S) range (2-0.01%) that is important for these polluted stratus clouds. Concentrations were usually characteristic of continental/anthropogenic air masses. The most notable feature was the consistently higher concentrations above the clouds than below. CCN measurements are so important because they provide a link between atmospheric chemistry and cloud-climate effects, which are the largest climate uncertainty. Extensive comparisons throughout the eleven flights between two CCN spectrometers operated at different but overlapping S ranges displayed the precision and accuracy of these difficult spectral determinations. There are enough channels of resolution in these instruments to provide differential spectra, which produce more rigorous and precise comparisons than traditional cumulative presentations of CCN concentrations. Differential spectra are also more revealing than cumulative spectra. Only one of the eleven flights exhibited typical maritime concentrations. Average below cloud concentrations over the two hours furthest from the coast for the 8 flights with low polluted stratus was 614?233 at 1% S, 149?60 at 0.1% S and 57?33 at 0.04% S cm-3. Immediately above cloud average concentrations were respectively 74%, 55%, and 18% higher. Concentration variability among those 8 flights was a factor of two. Variability within each flight excluding distances close to the coast ranged from 15-56% at 1% S. However, CN and probably CCN concentrations sometimes varied by less than 1% over distances of more than a km. Volatility and size-critical S measurements indicated that the air masses were very polluted throughout MASE. The aerosol above the clouds was more polluted than the below cloud aerosol. These high CCN concentrations from polluted air masses were affecting the clouds both from the air below and …
Date: February 27, 2009
Creator: Hudson, James G.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Primordial nucleosynthesis in inhomogeneous cosmologies:. cap omega. = 1 with baryonic dark matter

Description: We consider the constraints on ..cap omega.. from primordial nucleosynthesis in inhomogeneous cosmologies. We find that allowance for isothermal fluctuations significantly weakens the upper bound on the average value of ..cap omega.. derived from the standard big bang. Under the plausible additional assumption that regions of high baryon density are preferentially absorbed into cold dark matter, the constraints from primordial nucleosynthesis can be satisfied for large values of ..cap omega.., including ..cap omega.. = 1. 22 refs., 2 figs.
Date: September 1, 1986
Creator: Mathews, G. J. & Sale, K. E.
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Partner: UNT Libraries Government Documents Department
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D-T and D-D cycles for fusion-powered U-233 factories

Description: In spite of a low reaction parameter, the semicatalyzed D-D cycle constitutes an interesting alternative for symbiotic systems because it eliminates the need for blanket tritium breeding. Previous work on D-D fusion-fission hybrids concluded that blanket energy multiplication is low and that this cycle may be of interest for ignited plasmas only. Here, it is shown that low multiplication does not penalize the symbiotic system.
Date: January 1, 1979
Creator: Renier, J.P. & Martin, J.G.
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Partner: UNT Libraries Government Documents Department
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Higher superdeformed band members in sup 190 Hg: Evidence for a band interaction

Description: The superdeformed band of {sup 190}Hg has been traced up to a frequency {Dirac h} {ge} 0.4 MeV by combining data from several experiments. A distinct change in the slope of the dynamic moment of inertia J{sup 2} vs {Dirac h} is observed at {Dirac h} = 0.32 MeV. This result is interpreted as evidence for a band interaction at the highest frequencies. Possible interpretations are reviewed.
Date: January 1, 1992
Creator: Bearden, I. G.; Daly, P. J.; Janssens, R. V. F.; Carpenter, M. P.; Ahmad, I.; Khoo, T. L. et al.
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Partner: UNT Libraries Government Documents Department
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E4 Moments for Deformed Rare-Earth and Heavy Transitional Nuclei

Description: Techniques for measuring reduced matrix elements <4/sup +/ parallel M(E4) parallel 0/sup +/>, the interpretation of these data, and the implications for various nuclear models are reviewed and discussed. Actual examples are confined to deformed rare-earth and heavy transitional nuclei. 33 refs., 9 figs.
Date: August 1, 1987
Creator: Baker, F.Todd
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Partner: UNT Libraries Government Documents Department
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Ab Initio No-Core Shell Model Calculations Using Realistic Two- and Three-Body Interactions

Description: There has been significant progress in the ab initio approaches to the structure of light nuclei. One such method is the ab initio no-core shell model (NCSM). Starting from realistic two- and three-nucleon interactions this method can predict low-lying levels in p-shell nuclei. In this contribution, we present a brief overview of the NCSM with examples of recent applications. We highlight our study of the parity inversion in {sup 11}Be, for which calculations were performed in basis spaces up to 9{Dirac_h}{Omega} (dimensions reaching 7 x 10{sup 8}). We also present our latest results for the p-shell nuclei using the Tucson-Melbourne TM three-nucleon interaction with several proposed parameter sets.
Date: November 30, 2004
Creator: Navratil, P; Ormand, W E; Forssen, C & Caurier, E
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Partner: UNT Libraries Government Documents Department
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Time-dependent formalism for the decay of ground-state deformed nuclei by proton emission : a numerical challenge /.

Description: The numerical challenge associated with the time-dependent approach to the general problem of bi-dimensional quantum - tunneling is discussed and methods towards its application to concrete problems are developed.
Date: January 1, 2002
Creator: Strottman, D. D. (Daniel D.); Carjan, N. (Nicolae) & Rizea, M. (Margarit)
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Partner: UNT Libraries Government Documents Department
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Optimization of fusion-driven fissioning systems

Description: Potential advantages of hybrid or fusion/fission systems can be exploited in different ways. With selection of the /sup 238/U--/sup 239/Pu fuel cycle, we show that the system has greatest value as a power producer. Numerical examples of relative revenue from power production vs. /sup 239/Pu production are discussed, and possible plant characteristics described. The analysis tends to show that the hybrid may be more economically attractive than pure fusion systems.
Date: October 1, 1976
Creator: Chapin, D. L. & Mills, R. G.
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Partner: UNT Libraries Government Documents Department
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Effect of interacting particles on primordial nucleosynthesis

Description: We modify the standard model for big-bang nucleosynthesis to allow for the presence of a generic particle species, i.e., one which maintains good thermal contact with either the photons or the light neutrino species throughout the epoch of primordial nucleosynthesis. The production of D, /sup 3/He, /sup 4/He, and /sup 7/Li is calculated as a function of the mass, degrees of freedom, and spin statistics of the generic particle. We show that in general, the effect of an additional generic species cannot simply be parameterized as the equivalent number of additional light neutrino species. The presence of generic particles also affects the predicted value for the neutrino-to-photon temperature ratio.
Date: May 1, 1986
Creator: Kolb, E. W.; Turner, M. S. & Walker, T. P.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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The status of nuclear data evaluations for Version VI of ENDF/B

Description: A new version of the United States national evaluated nuclear data file, ENDF/B-VI, is nearing completion. Major emphasis is being placed on correcting some long-standing nuclear data problems that adversely affect applied calculations for fission and fusion reactors. This paper reviews some of the evaluation activities of most revelance for fission reactor applications, namely, those involving control, cooling, and shielding materials, structural elements, and the major actinides. Additionally, because of its impact on all the data, work on the Standards Data File for Version VI is also summarized.
Date: January 1, 1988
Creator: Young, P.G.
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Partner: UNT Libraries Government Documents Department
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The P-Factor and Atomic Mass Systematics: Application to Medium Mass Nuclei

Description: The P formalism was applied to atomic mass systematics for medium and heavy nuclei. The P-factor linearizes the structure-dependent part of the nuclear mass in those regions which are free from subshell effects indicating that the attractive quadrupole p-n force plays an important role in determining the binding of valence nucleons. Where marked non-linearities occur, the P-factor provides a means for recognizing subshell closures and/or other structural features not embodied in the simple assumptions of abrupt shell or subshell changes. These are thought to be regions where the monopole part of the p-n interaction is highly orbit dependent and alters the underlying single-particle structure as a function of A, N or Z. Finally, in those regions where the systematics are smooth and subshells are absent, the P-factor provides a means for predicting masses of some nuclei far-from-stability by interpolation rather than by extrapolation. 5 figs.
Date: January 1, 1988
Creator: Brenner, D. S.; Haustein, P. E. & Casten, R. F.
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Partner: UNT Libraries Government Documents Department
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Effective interactions, elementary excitations, and transport in the helium liquids

Description: Polarization potentials, the self-consistent fields which describe the primary consequences of the strong atom-atom interaction in the helium liquids, are developed for liquid /sup 4/He and /sup 3/He. Emphasis is placed on the common physical origin of the effective interactions in all helium liquids, and the hierarchy of physical effects (very short-range atomic correlations, zero point motion, and the Pauli principle) which determine their strength is reviewed. An overview is then given of the application of polarization potential theory to experiment, including the phonon-maxon-roton spectra of /sup 4/He and /sup 3/He-/sup 4/He mixtures, the phonon-maxon spectrum of normal and spin-polarized /sup 3/He, and the transport properties of superfluid /sup 4/He and of normal and spin-polarized /sup 3/He.
Date: January 1, 1986
Creator: Pines, D.
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Partner: UNT Libraries Government Documents Department
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The superfluid Stirling refrigerator, a new method for cooling below 0. 5 K

Description: A new subkelvin refrigerator, the superfluid Stirling cycle refrigerator, uses a working fluid of [sup 3]He-[sup 4]He mixture in a Stirling cycle. The thermodynamically active components of the mixture are the [sup 3]He, which behaves like a Boltzman gas, and the phonon-roton gas in the [sup 4]He. The superfluid component of the liquid is inert. Two refrigerators have been built and temperatures of 340 mK have been achieved.
Date: April 9, 1993
Creator: Brisson, J.G.; Kotsubo, V. & Swift, G.W.
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Partner: UNT Libraries Government Documents Department
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No-Core Shell Model Calculations in Light Nuclei with Three-Nucleon Forces

Description: The ab initio No-Core Shell Model (NCSM) has recently been expanded to include nucleon-nucleon (NN) and three-nucleon (3N) interactions at the three-body cluster level. Here it is used to predict binding energies and spectra of p-shell nuclei based on realistic NN and 3N interactions. It is shown that 3N force (3NF) properties can be studied in these nuclear systems. First results show that interactions based on chiral perturbation theory lead to a realistic description of {sup 6}Li.
Date: January 8, 2004
Creator: Barrett, B R; Vary, J P; Nogga, A; Navratil, P & Ormand, W E
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Partner: UNT Libraries Government Documents Department
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Superdeformation in the mass A {approximately} 80 region

Description: A new island of superdeformed nuclei with major-to-minor axis ratio of 2:1 has recently been discovered in the A {approximately} 80 medium-mass region, confirming the predictions for the existence of a large SD gap at particle number N,Z {approximately} 44. The general properties of more than 20 bands observed so far will be reviewed here, and compared with those of the superdeformed bands in the heavier nuclei.
Date: December 31, 1996
Creator: Baktash, C.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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